There are more cons than pros in later life, but more pros than cons for the developmental stages of life.
My parents wanted to start me in school early, but state laws wouldn’t let them. I had taught myself how to read (somehow. . .?) and they couldn’t keep me entertained enough at home. I needed more stimuli. When I finally did get to start going to school, I went to a private school and basically “tested out” of first grade and Kindergarten (whatever that means). I have half a year of Pre-K and half a year of Transition (or Primer, as it was called) and then straight to 2nd grade.
I absolutely hated my parents when I was 10 years old in the sixth grade and everyone made fun of me for being so young. I wasn’t a teenager until I started my freshman year in high school, and needless to say I was the last person in my grade to start driving. I was younger than most of the kids in the class below me. I HATED IT IN HIGH SCHOOL!
But, I went on to college right after I graduated, turned 17 just after graduation, and functioned all right. I couldn’t buy cigarettes and I still can’t buy alcohol for myself (2.5 months! woohoo!). I still look very young – I got carded to go see a rated R movie not too long ago – and I can’t go out with my friends to bars and clubs and places that have the 21 age requirement, so I have missed out on some social activites. I, too, tend to mingle with older kids anyway (and have since I started school), but they are now off doing things I am restricted from doing.
Lack of social activites up until 21 is the biggest consequence to skipping grades as a youngster, I believe, but I am accustomed to only having a few friends, and most of the time they accomodate my age problem (nope, I do not, have not, and will not get a fake ID: when I wanted one no one would make me one, and now that I am so close, its not worth the risk). The only real advantage I can see is that, if I wanted to take a few years off (and join the Peace Corps, which I was planning on doing before anti-American terrorism kicked into high gear) before I started my career, I wouldn’t be starting any later than most people.
So, to answer the OP, even though it wasn’t my decision, I don’t regret it and I think it was the best thing my parents could have done at the time.